For the 4th industrial revolution, on the basis of implementation of big data and a hyper-connected society, development of an electronic system capable of collecting information widely is required in place of limited information gathering method depending on vision, auditory, and tactile sensibility of a human being. An electronic nose, an electronic eye, and an electronic skin are devices imitating an olfactory system, a visual system, and a tactile system of a human being and are electronic devices distinguishing and characteristically analyzing odor, light, and temperature. Generally, the electronic nose, the electronic eye, and the electronic skin are terms for a gas sensor, an optical sensor, and a temperature sensor.
The electronic nose is an electronic device which is capable of accurately analyzing a gas. Recently, the need for development of a human welfare type electronic nose capable of analyzing environmental pollution due to volatile organic compounds (VOCs) and accurately detecting and controlling disease diagnosis in real time through respiration is increasing. While a human nose cannot distinguish between different odors in succession, the electronic nose has advantages in that various kinds of odors can be distinguished through a chemical sensor array and even trace amounts of a harmful gas can also be detected.
Generally, an n-type metal oxide semiconductor, such as TiO2, ZnO, SnO2, WO3, CrO3, or the like having a band gap of 2.5 eV or more and high charge mobility, is used as a material of the electronic nose. The electronic nose is operated because, when chemical materials, gases, and the like are chemically adsorbed on a surface of a metal oxide semiconductor, electrons move to the surface of the metal oxide semiconductor and thus electrical resistance is changed due to electron depletion.
However, since the resistance reaction due to the gas absorption of the metal oxide semiconductor is amplified by external heat energy, an additional heating device (a Joule heater) is required for a effective operation. The additional heating device has a problem of increasing a volume of the electronic nose device, lowering energy consumption efficiency, and increasing a manufacturing cost.
Therefore, it is required to develop an electronic nose which is operated at room temperature without an additional heating device. Further, in order to cope with an environmental change which is complicated and difficult to analyze, material and element technologies capable of obtaining and analyzing pieces of information on various environmental changes at once are required together with as electronic eye (optical sensor) and electronic skin (temperature sensor).
In particular, organic semiconductors and organic electrolyte materials are gaining attention due to being sensitive to the above-described various environmental changes and having excellent mechanical properties and room temperature driven characteristics.
However, a carbon-based organic material semiconductor and an ionic electrolyte have low charge and low ion mobility characteristics. Further, there is a problem to be solved in that the carbon-based organic material semiconductor is very vulnerable to a polar solvent such as moisture or oxygen due to the nature of the organic material.